The present invention relates to electrophotographic copying machines, of the kind including an endless image forming and transfer band of electrically conducting material having a photoconductive coating. In use, the band travels continuously and in succession past a charging station where it receives an electrostatic charge, an exposure station where an image of an original to be copied is projected thereon, a dusting station where toner powder is applied to the electrostatic image formed on the band at the exposure station, and a transfer station where the powder image is transferred from the band to a copy sheet.
Heretofore, transfer bands have had a seam produced by joining together, e.g. by welding, the ends of a strip from material of which the band is formed. However, no matter how carefully the joint is made, it constitutes a discontinuity in the band surface and thus complications are involved in ensuring that the exposure is made on the band without the image overlapping the joint. Thus, the present invention provides an electrophotographic copying machine which includes an endless and seamless image forming and transfer band made of electrically conducting material having a coating of a photoconductive material.
The band may have a thickness of 60 to 150 .mu., preferably 60 to 70 .mu., and is preferably made of metal, for example nickel, copper, a copper alloy or a nickel-cobalt alloy. It may be made by the galvanic deposition of the metal on a suitable form followed by stripping of the deposited metal from the form.
The photoconductive layer may be amorphous selenium, chalcogenite of antimony, lead, zinc, cadmium, mercury, lead iodide or an organic photoconductor. It may be deposited on the metal by electrophoresis, spraying, coating or dipping.